This invention relates to a ribbed tubular structure having a reinforcing rib connected to an outer surface of a tubular member providing a collapse resistant rubber structure and method of making the same.
Filament wound pipes or tubes have been fabricated by winding a tape or web of fibers impregnated with resin or other binder on a mandrel in a number of superimposed layers. After the desired number of layers have been wound on the mandrel to provide the physical properties required, the resin is cured to provide an integral structure which is then stripped from the mandrel. As one example of a filament winding machine as disclosed in U.S. Pat. No. 3,499,815 issued on Mar. 10, 1970 to R. Hof, a mandrel is mounted for rotation, and a winding head or carriage moves in a reciprocating path of travel along the mandrel and guides or winds the fibrous tape about the mandrel in a helical pattern. The fibrous tape is formed of a multiplicity of individual elongated filaments or fibers which are stored in coil form on creels. Such individual filaments are unwound during a winding operation and grouped to form the tape or web. Such tape is impregnated with resin and passed over a distribution roller or other guide member to be wound onto the mandrel.
In a filament winding operation, the fibrous tape may be wound in a helical pattern which can either be a crossover pattern or a sequential pattern. In the crossover pattern, the turns in each pass are spaced apart and the turns in succeeding passes are wound in abutting side-by-side relation to the turns of the preceeding pass. In the sequential pattern, the side edges of adjacent turns of each pass are disposed in generally abutting relation.
Light-weight and extremely durable pipes can be made from fibers or filaments of fiberglass, for example, which can withstand substantial predetermined internal pressure corresponding to a predetermined wall thickness. Such pipe, however, may be buried or submerged and subjected to substantial external pressure tending to collapse the pipe. Large diameter pipe may be designed with a wall thickness to adequately perform under moderate internal pressure, such as 50 to 100 pounds per square inch, for example, but which do not have sufficient stiffness to prevent collapse when submerged under body of water or buried within the earth, particularly when subjected to dynamic crushing forces such as provided by vehicular traffic, for instance.
One possible approach to overcome the collapsing problem of buried or submerged pipe is to wind additional filaments to uniformly increase the wall thickness throughout the entire pipe length. Such uniform increase in pipe wall thickness generally provides strength capabilities far exceeding what is customarily required for expected internal pressures provided by the conducted medium. While increased wall thickness throughout the entire pipe may eliminate the danger of collapse when buried or submerged, an extremely heavy or bulky pipe must be fabricated at an increase in cost.
Reinforcing ribs have been built up or placed along the outer surface of a pipe in order to increase the collapse resistance thereof and provide a relatively light-weight structure. Both semi-circular and hat shaped ribs have been provided such as by banding a plastic, rubber or paper rib form about a pipe which is thereafter overlayed with a glass cloth or fiber wrap impregnated with resin, such as illustrated in U.S. Pat. No. 3,737,353 issued June 5, 1973 to Gilbu and U.S. Pat. No. 3,457,963 issued July 29, 1969 to Hardwick. Many processes require considerable hand labor and are inefficient in time and expense in fabricating reinforcing ribs for tubular articles such as pipes.